63 gas gauge sender squawks

[petelempert]

I'm putting the gas tank back in my 63 and having some gauge sender unit issues. I decided to test the sender outside the tank, so I hooked up the single gauge power wire to the terminal post. I didn't think it needed a ground, but created one anyway to be safe by hooking a ground wire with one end to the frame and another to the ring that secures the sender. Keyed the ignition and the needle on the gauge swung to full...actually way past full...so far into full I can't even see it now. When I tested the float to see the range of motion, I got nothing. I figured maybe the ground was unnecessary, so I ditched that and still got nothing. Then I used my test light to see what was going on. With the test light grounded to the frame, the terminal wire showed no power. Then I switched the ground on my test light to the bumper and got a weak signal. All this time, still no movement on the gauge needle. In fact, I sort of miss the needle since I haven't seen it since I sent it into "full-land". Have I fried my sender, gauge, both? I don't think there is a ground to the tank...didn't see it in the manual. Why does the needle not swing back to empty when I un-key the ignition? What am I missing? Thx PRL

[1965rivgs]

The sending unit needs to see a good ground to work properly. The Rivs dont have a dedicated ground wire, some cars do. In the Riv the ground is completed thru the fuel tank mounting straps. Cant hurt to have an extra ground wire though.

Your description of having ground at the bumper but not at the frame does not make sense as the bumper is grounded thru its mounting to the frame. So, something is wrong there. If you have ground at the bumper you should have ground on the frame. Maybe you failed to achieve a proper ground on the frame thru a bad troubleshooting connection?

This circuit is a low voltage circuit, not full system/battery voltage. Some cheap test lights do not have a low enough threshold voltage level to light the bulb when checking low voltage circuits. Best to use a DVOM.

Your dim light is encouraging in that it indicates that you have the proper reduced voltage at the sender from the gauge. So, your circuit is good thru the gauge back to the sender. That doesnt mean the gauge is good, just that there are no opens or shorts in the circuit.

Cant recall if the Riv gauge is wired to go full when the sender wire is grounded or empty, both scenarios are possible, but that doesn`t matter at this point.

To check the gauge, WITH THE KEY ON, ground the sender wire. The gauge should either go full or empty. no in between. Conversely, when the wire is removed from ground, with the key still on, the gauge should peg in the opposite direction. If your gauge does not respond like that the gauge is most likely bad. Be sure you have a good ground when testing!

If the gauge checks OK there are a few ways to check the sender. You can use an ohmeter to check resistance or simply connect it to the sender wire, be sure it is properly grounded and manipulate the float while checking the gauge. I prefer the ohm meter method because it isolates the sending unit

Connect one probe to the terminal where the sender wire connects. Connect the other probe to the sending unit body or top plate. With the float in the highest position you should show a resistance level. As the float is dropped the resistance level should become greater until it tops out at full float drop. Be careful as you manipulate the float arm as the contact arm may have intermittent contact with the grid if you torque the arm from side to side in any way, they are sensitive!

Common problems are a broken strap (you`ll see it) and the "grid" contained in the unit under the stamped steel cover can varnish over interfering with contact.

The system is quite simple when one is familiar with the basics. This is a situation where good common sense and success go hand in hand. Be sure you have good troubleshooting connections! Hope this helps,

Tom Mooney

[petelempert]

T-Thanks. Tonight, I'm going to try to get a better frame ground. You are right, the bumper should be as grounded as the frame. First, I'lll see if i can get the needle to swing back and forth. We'll see. Next, I'll try the ohm meter. The sender itself looks good, but it's been pulled around a lot in the last few weeks with all the work I've been doing to the tank. Thx PRL

[petelempert]

T-You were right...I had a bad ground on the frame. Tonight, I made sure the ground was clean, hooked up the sender and guess what...it worked. Thanks a million, I was starting to think I'd need to use a stick in the tank like the old days to figure out how much gas I had. Here's two more questions for you: Since I now have a solid ground on the frame, should I continue to use that new ground or rely on the straps to function as ground. If I use the new ground, can I attach it to the ring that secures the sender to the tank? Also, I want to use a rubber mat between the tank and the trunk to insulate for sound and chaffing...will that affect my ground? Thx PRL

[Jim Cannon]

I recommend you add a dedicated ground. You can never have too many grounds. They do not interfere with each other or anything. They all work together to make sure you have a good ground, no matter what.

The straps would theoretically still provide ground with a rubber mat between the tank and the underside of the trunk, as long as the straps have a good contact with the bottom of the gas tank.

I still recommend you add a dedicated, direct ground from tank to frame.

[petelempert]

Thanks Jim. I'm going to ground it to the frame, put the rubber mat in and hang the tank tonight. I'll gas it up over the weekend and see what happens. BTW, did you ever notice that the OD on the pickup tube in the gas tank is actually larger that 3/8"? I wanted to put a filter/strainer/sock on the pickup tube (my car did not have one when I opened it up) in this process. Had a hard time finding one at the standard parts stores. Finally ordered a 3/8 online and had to "coax" it to fit. I assume the car came with an in-tank filter when new...wasn't sure if the slightly larger OD tube is Riv specific. Thoughts? PRL

[Jim Cannon]

I don't know.

[1965rivgs]

Pete, why dont you post a part number and manufacturer for the tank filter for the benefit of those who would like to replace theirs? Personally, I`m not particular about the presence of a tank filter or not but most folks are and might find the info helpful,

Tom Mooney

[bepnewt]

I'd also like to see some info and a pic if possible on the rubber mat if you have the time, please.

I'll be dropping my tank soon and would like to do as much as I can while it's out.

Thanks,

-BEPNewt

[petelempert]

The filter is an ACDelco 3/8" tank filter that I actually ordered from YearOne. I don't have the box anymore, or the part number but apparently they were GM OEM issued from the mid sixties into the seventies. I also noticed OPGI features them in their latest catalog. I have a 442 that I put the same YearOne sourced Delco 3/8" filter in the tank several years ago. On the Riv, the pick-up tube in the tank measured approximately 3/8" OD but I had to gently coax it to fit. I put a carpenters plumb bob in a vise with the point sticking out. Then I gently took the filter and pressed the end against the conical part of the plumb bob. The result is that it opened the fitting slightly so that it would fit snugly on the pick-up tube and not fall off inside the tank. So far, it seems to be working great.

Regarding the mat, I sort of went way off the reservation on this one. I checked with companies like Quanta Products and found expensive rubber/foam mats die-cut to fit specific cars, but not a 63 Riv. The more I thought about it, I really just needed some rubber that would prevent chaffing, insulate a little and not melt. So...I bought a cheap large black floormat...cut it to size and slid in in between the tank and the underside of the trunk. Does it work? Heck yeah. Can you see it? Heck no...I'm the only one who knows it's there.

All of this stuff with tank filters, sender units and trunk mats is part of a gas tank experiment I've been messing with for two months. I was having major fuel contamination issues...basically pulling rust particles out of my carb for the last two years. I narrowed the culprit to my tank. I didn't trust another used one. I didn't want to build a custom tank. I didn't want to mess with liners. I was convinced my tank was the devil and was willing to go to extremes to solve the problem. So, I researched and found a reproduction GM tank from Quanta Products that was really close in dimension to the 63 Riv. It was 1/4 the cost of a custom tank. I grafted the sender receptacle from my old tank on the new one and revised the filler neck on the new one to fit. I know a talented welder who made this possible. Guess what...it worked...I put it all together last night and it works great. It looks completely stock, the gauge works well...it's awesome. You guys should let me know if there is interest in this experiment, because I'd be glad to share pictures, part information etc. PRL

[RivNut]

You bet your bippy we're interested. What vehicle is the new tank an actual replacement for? What did you have to do to the filler neck? And what did you have to do to graft the sending unit to the new tank. Anxiously awaiting your reply (with pictures if handy.)

Ed

[tim63riv]

Guys,

The in tank filter, sometimes called a fuel sock, is supposed to have a VERY tight fit on the pick up tube, it doesn't help you if it is rolling around the bottom of the fuel tank. As far as the rubber sheet between the tank and floor, I have some mixed ideas on that one. Being from a rust belt state, I wouldn't go this way because of condesation issues. That rubber might deaden some noises from the fuel tank, but is going to hold condensation against the top of the tank and the bottom of the trunk floor! The tanks are designed to have a gap above them so that air can pass through and dry out the area between the tank and floor as the car is driven.

The extra ground wire is always a good idea.

My 2 cents,

Tim